Opto-matrix frames have been developed which utilize rows of light sources such as phototransmitters and light detectors such as photoreceptors in X and Y arrays to effectively cover a given area with light beams which, when broken by the insertion of a stylus such as a finger, provide an electronic signal or signals useful to indicate X-Y location of the stylus. Such frames have found widespread use in touch input or touch screen entry devices wherein the frames are fitted over the information display devices of computers and the like. U.S Pat. No. 4,267,443 titled "Photoelectric Input Apparatus" issued May 12, 1981 to Carroll et al. relates to the use of an opto-frame. Large opto-frames have also been conceived for providing security or safety in order to alarm or arrest the movement of machinery so as to prevent entry in unauthorized areas as for example, by the hand of an operator of a punch press relative to the closure of dies in the press.
As a general rule, the cost and complexity of opto-frames has heretofore been proportionate to the number of phototransmitters and photoreceptors employed which number is proportionate to the size of the area to be covered and the resolution desired. As a general rule, the closer together physically the light elements are, the higher the resolution or the ability to distinguish coordinate locations of a stylus or finger or the like penetrating the light beam array. Also as a generalization, the largest part of the cost of opto-frames is for the photoreceptor and phototransmitter devices and associated drive circuits.
With this understanding as background, it is an object of the present invention to reduce the cost of opto-frames by reducing the number of phototransmitters from that heretofore utilized. It is a further object of the invention to reduce the complexity and cost of opto-frames and other area scanning optical systems for detection and coordinate location purposes by substituting reflecting means for numbers of phototransmitters as heretofore employed. It is still a further object of the invention to reduce the numbers of phototransmitters and photoreceptors in applications of light beam area coverage wherein the presence of a stylus or other element breaking such beam must be detected It is a final object to provide a novel technique of reflecting light for a variety of purposes.